Aqua Sphere is a brand of Italian swim goggles. Compared to classic swim goggles, they look funny. Instead of the common double-cup design, they have a single broad frame that embraces the face with a flanged silicone skirt. They look like a pair of ski goggles flattened.

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To the swimmer, this design has advantages. The force exerted by the straps is comfortably distributed over a wider area of the face. The soft grab of the skirt minimizes leakage. The flatness reduces drag. And if the swimmer in the next lane errantly bats the frame, a cup doesn’t flip over to drive a convex solid into the eyeball.

I bought my pair of Aqua Spheres for $23 at Sports Basement, a discount sporting goods store in San Francisco. But ten blocks away at a triathlon boutique, the same model costs $30. Of course, both work the same. Same comfort, same watertightness, same streamlined shape. Perhaps obviously, price has no effect on quality.

Now imagine a situation where this highly functional product starts to rise in price. Suddenly, no Aqua Sphere goggle is available anywhere in California for less than $35.

Swimmers start to rationalize this. Because they’re made in Genoa. Because Olympians use them. Rumor takes hold.Because they’re going to stop making them. Aqua Sphere develops a rarified, elite reputation.

Bloggers pick up on this sentiment. They seize on previously overlooked virtues.They’re tested in the Mediterranean. Royals love them. Fitness product reviewers uncover links between the single-frame construction and sexual magnetism. Supermodels have a different pair for each swimsuit. Demand soars. Unemployment in Genoa disappears.

Now imagine the opposite. Instead of rising in price, Aqua Spheres plunge in price. First, the triathlon boutique matches Sports Basement at $23. Then the boutique stops carrying them entirely, closing out its remaining inventory at $19. Aqua Sphere goggles start showing up in drugstore bargain bins with red $9.99 price tags slapped on the mirrored plastic lenses.

The chatter among swimmers changes. They’re not classic. They look weird. The Salvation Army notes a curious spike in Italian swim goggle donations. Suddenly, no one wants to be caught dead in those things.

Silly? Well, to the extent that sports products follow fashion trends, the scenario is conceivable. Demand for particular models of swimsuits, for example, certainly ebbs and flows with changing tastes.

But performance swim goggles may be more of a technical product. They’re judged on their merits. Aqua Spheres have an objective set of characteristics that most competent swimmers appreciate. They’re more comfortable. They leak less. They’re streamlined. For these straightforward reasons, they’re exceptional.

What about companies? Are they subject to fashion trends, or are they judged on their merits? Surely they too have characteristics that speak to their value. And yet sentiment often swings because of stock price movements.

Some companies are superior. They have outstanding operating results, solid strategic positionings, and a shareholder-friendly orientation. Often these companies are priced fairly. But sometimes, their price soars. Others times, it plunges. But their value isn’t impacted by price swings any more than Aqua Spheres get leakier when they go on sale.